DefinitionA cancer is a group of abnormal cells, known as a tumour, that grows uncontrollably. Cancerous tumours invade and destroy surrounding tissue. Not all tumours are cancerous. Benign tumours, which are not cancerous, do not invade and destroy tissue. However, a benign tumour may grow very large. Cancerous tumours may shed cancer cells that spread to other parts of the body, which is called a metastasis. Benign tumours do not spread in this way.

What is going on in the body? The genetic material within the nucleus of the cell that provides the "blueprint" that directs normal cell function is known as the chromosome. The nucleus, which houses the chromosomes, is the control centre for the cell. The nucleus of a normal cell such as a muscle cell, controls its activity as part of a larger tissue, a muscle. The cell will then act in concert with other cells of that muscle to expand and contract causing motion. Damage to the nucleus causes the cell to lose the ability to behave normally.

Cancer occurs when the damage causes changes that make the cell grow and divide uncontrollably. When a cell becomes cancerous, a tumour eventually forms from these abnormal cells. Because the tumour is made up of defective cells, it cannot serve the function of the tissue from which it arose. The body suffers from both the loss of the normal function of that tissue as well as the damage to other tissues. For example, when a cancer replaces the liver tissue, the body cannot filter wastes properly.

A cancer is named according to the type of organ tissue from which it developed. For example, breast cancer will always be called breast cancer, even if it spreads to other body parts. The specific type of tissue within an organ that underwent the cancerous change also further identifies a cancer. For example, lung cancer is grouped into several groups depending on exactly what kind of lung tissue was affected. A cancerous tumour does not grow any faster than the kind of tissue from which it started. It will continue to grow and multiply uncontrollably. Normal tissue does not grow continually.

In the early stages of any cancer, there may not be much visible effect on the body. Cancer cells can break off from the main tumour and travel through the blood stream to other parts of the body. These cancer cells may then form new tumours, known as metastases. As the cancer grows and spreads, or metastasises, the person will likely begin to weaken. Cancer places many demands on the normal functioning of the body.

In the advanced stages, symptoms such as weight loss, weakness, and fatigue are common. At the same time, new cancerous tumours that spread to other parts of the body may cause other organs to fail. If not successfully treated, the cancer will cause the person to die by destroying the functioning of vital body systems.

These vital body functions include:

breathing, when the lungs are involved

waste removal, when the liver or kidneys are involved

regulation of body functions, when the brain is involved

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Most cancers occur in people older than 55 years. This may be because cells become more vulnerable to damage after years of use. It is possible for children to have cancer, but this is rare. More men than women have cancer. The most common cause of cancer death in men and women is lung cancer.

What are the signs and symptoms of the disease?The specific symptoms of cancer depend upon where the cancer is located. In some cases, a tumour can remain hidden for years because it causes no damage to tissues that would result in an observable symptom. For example:

A bowel cancer may be undetected until it erodes into a blood vessel in the colon. Blood will then leak into the stool.

Many times the symptoms of cancer are vague or can be mistaken for other diseases. The non-specific symptoms of cancer can include:

fatigue

unusual lumps or growth

unexplained weight loss

persistent cough

abnormal discharges

All these symptoms should prompt a person to see a doctor.

What are the causes and risks of the disease?For cancer to occur, something must damage nucleus of the cell. Some people are born with a predisposition to cancer. Their cells may be more vulnerable to the kind of damage that leads to cancer. For others, the damage occurs after years of exposure to substances that can cause cancer. Tobacco from any source is very dangerous. Certain chemicals, unprotected sun exposure, and radiation can all cause serious damage.

What can be done to prevent the disease? Cancer found early is much easier to treat. Some cancer prevention steps include:

Avoiding all tobacco products will help prevent the major causes of cancer death, lung cancer.

Limiting sun exposure, especially in children, will help prevent melanoma.

Eating a diet high in fibre may help reduce the incidence of bowel cancer.

Avoiding alcohol ingestion.

Regular medical checkups

testicular self-examination for men

breast self-examination for women

Since some cancers cannot be prevented, early detection and diagnosis are important keys to improving cancer survival.

How is the disease diagnosed? If cancer is suspected, it must be confirmed by examining the abnormal tissue in the pathology laboratory. This can mean removing a piece of the tissue with a biopsy. Sometimes the whole tumour is removed, which is known as a re-section. Additional studies such as specialised X-rays and blood tests may be performed to measure the extent of the disease, which is known as staging the disease.

What are the long-term effects of the disease? If cancer is not successfully treated, it will be fatal. Half of all people with cancer are cured with treatment. Cancer can often be successfully controlled even if it is not cured.

What are the risks to others?There is no risk to others from people with cancer. Cancer cannot be spread from one person to another.

What are the treatments for the disease? Treatment for cancer may require using many forms of treatment. Some of these include:

Surgery-removal of the solid tumour. Surgery is the first treatment for many cancers. If the tumour is small enough then the cancer can often be cured this way. Since this is considered a local treatment, surgery is not effective for cancer that is spread to other parts of the body. Leukaemia and lymphoma that involve the blood system cannot be treated by surgery because these cancers are not localised.

Chemotherapy-a type of treatment that involves the use of medications. The medications are introduced into the body and then are transported throughout the body through the bloodstream. This is considered a systemic treatment because the medications may affect the whole body. This approach has been used to cure or control certain cancers that are not localised. Not all cancers are sensitive to chemotherapy in much the same way some infections do not respond to antibiotics.

Radiation, a local treatment that involves the use of very focused energy waves of radiation directed at tumours. This can kill or slow the growth of many cancers. In some cases it may cure certain cancers if they are localised and sensitive to radiation. Examples of cancers cured by radiation are Hodgkin's disease and cancer of the voice box, or larynx.

Immunotherapy-using the body's immune response to kill or control the cancer. It has only limited effectiveness. It is useful only for certain cancers. Many cancers are too advanced at diagnosis to be effected by this approach alone.

In many cases, a combination of treatments has proven most effective.

What are the side effects of the treatments?The side effects depend on the type of treatment and the extent of treatment.

Localised therapy may have minimal side effects.

Extensive surgery or intensive chemotherapy may require a long recovery period. Current management of side effects make it possible for many people to maintain normal activities throughout the treatment period.

In advanced cancer, treatment is aimed at improving quality of life and decreasing symptoms of the cancer.

What happens after treatment for the disease?After treatment, the person with cancer will be monitored closely to determine the effectiveness of treatment. People who are cured of their cancers should be able to resume normal lives. If the treatment is not effective, other therapy may be tried. If all therapy has proved ineffective, every effort will be made to assure comfort during the final stages.

How is the disease monitored?The cancer will be followed according to type and how it was diagnosed. A leukaemia will be followed by examining blood samples. A lung cancer will be followed by specialised X-rays of the chest if it was visible at diagnosis. Progression of an advancing cancer may be monitored through X-rays depending where the cancer has spread or is suspected to have spread.

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